To ask at what age do you have "The Sex Talk" with your dc?

[Itsnotahoover]

I have an almost 7 year old ds and I'm always honest with answers to any questions, however, he hasn't asked many as yet. He's asked how babies get out of their mummy's tummys but not how they get in there in the first place!

Now I know they are covering anatomy and relationships at school, but I'd rather him hear the facts from me before he gets to that stage of lessons at school/hears idle gossip in the playground, but is there an age where it's best to sit them down for a chat? Or are there any good books I can just casually drop into his book box?

And yes, this is inspired by another thread, but it's something I've been wondering about for a while :)

I'm waiting for DD (7) to ask, but not leaving it too long like we did with our eldest DS.. Cocked up a bit there tbh and he heard alsorts in the playground, put 2 and 2 together and made about 45!
It culminated in a rather embarrassing conversation while waking through the park and him asking me what a vagina was while walking past a group of old ladies... Lesson learnt!